CVE-2025-71359
picklescan before 0.0.29 fails to detect malicious pickle payloads that utilize lib2to3.pgen2.grammar.Grammar.loads in the reduce method, al
CVSS
8.1
High
EPSS
0.4%
p35
KEV
—
Exploit Today
10
0-100
Published: Jul 4, 2026 · Last modified: Jul 6, 2026 · CWE-502
0.4%EPSS · 30 days0.4%
2026-07-042026-07-19
picklescan before 0.0.29 fails to detect malicious pickle payloads that utilize lib2to3.pgen2.grammar.Grammar.loads in the reduce method, allowing remote code execution. Attackers can craft pickle files embedding dangerous code that evades picklescan detection and executes during pickle.load() deserialization.
- github.comhttps://github.com/mmaitre314/picklescan/security/advisories/GHSA-f54q-57x4-jg88
- www.vulncheck.comhttps://www.vulncheck.com/advisories/picklescan-unsafe-deserialization-via-lib2to3-pgen2-grammar-grammar-loads
- github.comhttps://github.com/mmaitre314/picklescan/security/advisories/GHSA-f54q-57x4-jg88
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——29An undocumented and unsafe feature in the PLY (Python Lex-Yacc) library 3.11 allows Remote Code Execution (RCE) via the `picklefile` parameter in the `yacc()` function. This parameter accepts a `.pkl` file that is deserialized with `pickle.load()` without validation. Because `pickle` allows execution of embedded code via `__reduce__()`, an attacker can achieve code execution by passing a malicious pickle file. The parameter is not mentioned in official documentation or the GitHub repository, yet it is active in the PyPI version. This introduces a stealthy backdoor and persistence risk. NOTE: A third-party states that this vulnerability should be rejected because the proof of concept does not demonstrate arbitrary code execution and fails to complete successfully.5d